In magnetic random access memories (MRAMs), memory cells are arranged in arrays having rows and columns. In some approaches, with reference to an accessed memory cell selected from a row and a column, a sense amplifier is used to compare a current flowing through the accessed memory cell against a reference current. Ideally, the value of the reference current is averaged between the currents when the accessed memory cell has corresponding high and low logic values. To that end, two reference cells are used, one having a low logic value, and one having a high logic value.
Effectively, the sense amplifier receives one accessed memory cell at one input and two reference cells at another input, and is therefore not symmetrical. As a result, the sense amplifier experiences unbalanced parasitic decoupling during a transition period after the sense amplifier is turned on, which, in turns, requires a long wait time for the currents at the two inputs of the sense amplifier to be stabilized. Further, the capacitive loads at the two inputs of the sense amplifier are not equal, and cause inaccuracies in fast dynamic sensing when instantaneous current difference is detected and amplified.
At high temperature such as 85° C., non-selected cells in two columns containing the reference cells have twice higher leakage current than non-selected cells in a regular column containing an accessed memory cell. As a result, a higher leakage current in the reference columns favors sensing a high logic value and contributes an error when sensing a low logic value.
Like reference symbols in the various drawings indicate like elements.